1. Field of the Invention
This invention relates to the field of suspensions for disk drives. More particularly, this invention relates to the field of electrical connections within disk drive suspensions.
2. Description of Related Art
Magnetic hard disk drives and other types of spinning media drives such as optical disk drives are well known. A disk drive suspension is the assembly that aligns the read/write head over the correct place on the spinning data disk, in order to write data to, and read data from, the desired data track on the disk.
Both single stage actuated disk drive suspensions and dual stage actuated (DSA) suspension are known. In a single stage actuated suspension, only a voice coil motor moves the actuator arm with the slider affixed to the distal end. In a DSA suspension, as in U.S. Pat. No. 7,459,835 issued to Mei et al. as well as many others, in addition to the voice coil motor which moves the entire suspension, at least one secondary actuator, often referred to as a microactuator, is located upon the suspension in order to effect fine movements of the magnetic head slider thereby maintaining proper alignment over the appropriate data track on the spinning disk. The microactuator(s) provide much finer control and a higher bandwidth of the servo control loop than does the voice coil motor alone which is capable of effecting relatively coarse movements of the suspension and hence the magnetic head slider. Lead zirconium titanate is one of the broadly used intermetallic inorganic compounds possessing piezoelectric properties and is commonly referred to as PZT. PZTs are often used as the microactuator motor, although other types of microactuator motors are possible.
Various structures and methods have been proposed for making the required electrical connections to the PZT microactuators. One structure and method is to bond a gold plated copper contact pad that is part of the suspension's flexible circuit to a gold plated (metalized) surface of a PZT using conductive epoxy.
In the discussion that follows, it will be assumed without explicitly reciting that the copper contact pad is coated with gold or some other protective metal, and that the PZT surface is metalized with gold or some other relatively non-corroding metal.
Another structure and method is disclosed in U.S. Pat. No. 8,570,688 issued to Hahn et al, which is owned by the assignee of the present invention. That structure and method use a stainless steel spring to press the copper contact pad against the PZT surface optionally with conductive grease between those two surfaces, and/or with a protective pad between the spring finger and the contact pad in order to eliminate or reduce fretting. The copper contact pad and the PZT's electrode are thus physically pressed together and physically held together. The conductive grease enhances the electrical connection between them. In that proposal the bias pressure provided by the spring eliminates the need for conductive epoxy between the two parts.
The industry continues to seek ways to improve the quality of the electrical connection to the PZT microactuator, to improve the reliability of that connection, and to reduce the cost of making it.